Traction devices for elevator systems are known per se. Ropes as well as belts are often used and as belts, flat belts, multiple V-ribbed belts or even toothed belts are utilized.
For ropes as traction devices, each individual rope is clearly assigned its own rope groove on the traction sheave. Each rope engages into the corresponding rope groove by at least a portion of its diameter. Each individual rope is an independent traction element and can also be driven individually. For higher loads, either several ropes can be used in parallel or the rope diameter is correspondingly increased. The individual rope is therefore not only traction means for transferring the tension forces but also participates directly in the transfer of the traction forces.
Compared to belt technology, ropes afford the advantage that the force is directly transferable from the traction sheave to the rope. In belt technology, the connecting elastomer material lies between the actual tension carriers and the traction sheave.
When belts are used, several mutually adjacent lying ropes as traction elements are always embedded in a common belt body. The traction elements are completely encased in the basic material of the belt body and the plane of the traction element lies above the contact plane which the belt forms with the corresponding belt sheave. In toothed belts, the belt teeth can be viewed as the contact plane and in V-ribbed belts, the wedge plane can be viewed as the contact plane and in flat belts, the flat belt surface can be directly viewed as the contact plane.
The traction elements are therefore exclusively responsible for transferring the traction forces. For higher loads, wider belts or belts of a higher capacity class can be used with larger belt division and stronger tension elements.
The belts are basically clearly wider than high in order to ensure a stable belt running on the sheave.
European patent publication 1 396 458 A2 describes an elevator arrangement wherein a flat belt of elastomer material is used as traction means with the flat belt being reinforced with reinforcement elements. United States patent publications 2007/0084671 and 2009/0166132 disclose an elevator facility having a V-ribbed belt.
Compared to ropes, belts afford the advantage that, on the one hand, the manipulation is easier because individual ropes do not have to be placed on the corresponding grooves of the traction sheave. Also, small traction sheave diameters can be used because the embedded reinforcement mostly has a small diameter. Furthermore, belts as traction means are virtually free of maintenance because no lubrication is required.
In addition to friction between traction sheave and elastomer, the transferable force is, however, also dependent upon the quality of the embedment of the reinforcement in the elastomer, that is, on the adherence capability between elastomer and reinforcement as well as upon the shearing strength of the elastomer.
Furthermore, at least two and as a rule, three to five, belts must be used in parallel, for example, in elevator systems for reasons of safety. The belt compared to a rope of the same strength is relatively wide because the belts contain a plurality of thin individual ropes. If now several belts are utilized in parallel, relatively wide traction sheaves and direction-changing sheaves are required.
In U.S. Pat. No. 6,739,433, traction means are disclosed for an elevator system which is configured as a profiled flat belt so that the surface, which is available for friction between the traction sheave and the belt, is somewhat greater. The transferable force is thereby somewhat higher than for a non-profiled flat belt. However, here too, the zone of the force transfer between the traction sheave and the traction means is still significantly spaced from the reinforcement so that the elastomer material of the flat belt is subjected to a relatively high shear.